Current ruminant feeding practices rely heavily on readily fermentable carbohydrates and chopped, ensiled forages. Such feeds generate acid in the rumen which is not counterbalanced by dietary or endogenous bases and buffers. Under acidic conditions, the population of microorganisms found in the rumen are less desirable than those found under neutral or slightly basic conditions. Under neutral or slightly basic conditions, rumen microorganisms produce more fatty acids, which can be used by the lactating animal to produce milk fat.
It is known that sodium bicarbonate and magnesium oxide, alone or in combination, are effective in increasing the milk and/or milk fat production of animals fed on high acid-producing diets. Chalupa and Kronfeld, 1983, Animal Nutrition and Health, May-June, 50; Erdman, et al. 1982, Journal of Dairy Science, 65, 712; Erdman, et al. 1980, Journal of Dairy Science, 63, 923; and Kilmer et al. 1980, Journal of Dairy Science, 63, 2026. However, these additives have the undesirable effets of temporarily reducing the feed intake and decreasing the serum levels of potassium and magnesium.